1. Field of the Invention
The present invention relates to an automatic sheet feeding apparatus for automatically feeding sheets one by one.
2. Related Background Art
Recording systems such as printers, copying machines, facsimiles and the like have been designed so that an image comprised of a dot pattern was formed on a recording sheet such as paper, plastic film and the like by driving energy generating means of a recording head in response to image information. Such recording systems can be grouped into ink dot recording type, wire dot recording type, thermal type, electro-photographic type and the like in accordance with the recording modes. On the other hand, recording sheets used with the recording systems may include a thicker sheet such as a post card, an envelope or the like, and a special sheet such as a plastic film or the like, as well as a plain paper sheet. The recording sheets have been supplied one by one in a manual supply mode, or sequentially in an automatic supply mode by automatic sheet feeding apparatuses.
FIG. 36 is a perspective view of a conventional recording system B on which an automatic sheet feeding apparatus A is mounted, and FIG. 37 is a perspective view showing the construction of the conventional automatic sheet feeding apparatus A. As shown in FIGS. 36 and 37, the automatic sheet feeding apparatus A generally includes a sheet supply drive portion comprising left and right sheet supply rollers 101, 102, a sheet supply shaft 106 and a drive gear 107, and a sheet supply cassette portion stacking sheets and comprising left and right side guides 103, 104 and a pressure plate 105, and is so designed that the sheets are separated one by one by means of left and right separating claws or pawls 109, 110 and of the sheet supply rollers 101, 102 driven by a driving force from a sheet feeding mechanism of the recording system via the drive gear 107 and supplied to guide member 111. A release lever 108 is also provided to control a pressure force applied to the stack of sheets.
However, the above-mentioned conventional sheet feeding apparatus has the following drawbacks, since the sheet separating means such as the sheet supply rollers 101, 102 and the separating claws 109, 110 are disposed in pairs at the left and right:
(1) The construction becomes complicated, and the number of parts is increased, thus making the apparatus expensive; and PA1 (2) Since a space through which the sheet supply shaft 106 passes must be reserved, the apparatus becomes large-sized.
To eliminate these drawbacks, the technique in which a separating claw and a sheet supply roller are arranged only at one side of the apparatus has been proposed, as disclosed in U.S. Pat. No. 4,372,547. In this case, however, since the sheet is skew-fed, a skew-feed preventing roller must be additionally provided (see the above U.S. Pat. No. 4,372,547). Accordingly, even with this technique, the cost of the apparatus cannot be reduced satisfactorily.